In this type of torque measuring device the automatically balancing throttle locations bring the supplied pressure medium current, for example, especially oil current, to a measuring pressure which is proportional to the exerted torque.
Known hydrostatic torque measuring devices of the above-mentioned type employ a multi-chambered rotary piston, which is moved by the rotation of the input and output shafts and closes off or exposes valve openings in the side wall proportionately to the angle of rotation in such a manner that a compressive force is built up in the corresponding piston chamber, which is in equilibrium with the applied torque.
The achievement of a frictionless rotary piston, however, faces several difficulties, yet must be guaranteed very tight tolerances on two diameters with perfect concentricity. In addition, the localized throttling results in a large elasticity between the drive and output shafts and to an angle discontinuity when there is a failure of the hydraulic measuring fluid; both phenomena can lead to a destruction of the measuring device or the installation.